It is current practice to dry grain or other like materials by placing same in a cylindrical container and forcing heated air upwardly therethrough. Various methods, such as batch drying and layer drying have been developed to overcome problems encountered in such drying operations. Both such methods are inefficient since considerable time and labor is required. Additionally, problems such as uneven drying, incomplete drying, and crusting of the upper surface further complicate such drying operations and may result in insect infestation and/or spoilage. A more efficient method is deep-bed drying, wherein the container or bin is substantially filled with grain and a stirring device, such as that disclosed in U.S. Pat. No. 3,251,582 and U.S. Pat. No. 3,580,549, is used to constantly stir or mix the grain throughout the drying cycle. Such devices are normally constructed to travel a predetermined path circumferentially and radially within the container during the drying cycle thereby overcoming the above problems.
A new problem has arisen, however, in the case when a stirring device operates in a stationary position for a substantial length of time. Such operation results in overstirring and possible damage of grain surrounding the mechanism. With the typical two motor grain stirring mechanism in which a first motor drives the stirring unit in an orbital and radial path around the bin, and a second motor powers the stirring mechanism, the above-described problem can occur as a result of failure of the first motor, malfunctions in the drive linkage, or obstructions.
Unlike prior art systems, the present invention provides an apparatus for continually monitoring the orbital movement of the stirring mechanism support structure and automatically powering off the motors in the absence of orbital movement after a predetermined time period. In this manner the present invention avoids needless damage to the material contained within the container and conserves electrical energy for more productive uses.